1. Field of the Invention
The present invention relates to a laminated ceramic electronic component, such as a laminated ceramic capacitor. More particularly, the present invention relates to a laminated ceramic electronic component in which an internal electrode extended portion includes a thick film portion whose film thickness is relatively large.
2. Description of the Related Art
The size of portable electronic apparatuses, such as cellular phones or digital cameras, has been increasingly reduced. Therefore, for laminated ceramic electronic components, such as a laminated ceramic capacitor, used in a portable electronic apparatus, a reduction in size and an increase in precision have been demanded. For example, in a laminated ceramic capacitor, the thickness of a ceramic layer between internal electrodes connected to different electric potentials has been reduced to be about 3 μm or less.
External electrodes of the laminated ceramic capacitor are formed by applying and printing a conductive paste onto the ends of a ceramic element assembly. In the external electrodes, the conductive paste tends to predominantly adhere to the center of the end surface of the ceramic element assembly when the conductive paste is applied. Therefore, the external electrodes are partially thick on the end surfaces of the ceramic element assembly, and the thickness may exceed about 30 μm. Therefore, even when a reduction in size of the ceramic element assembly has been attempted, the external dimensions of the laminated ceramic capacitor have been increased.
In view of the above-described problems, WO 2007/049456 discloses a method of forming external electrodes on the end surfaces of the ceramic element assembly by directly performing plating thereon. In WO 2007/049456, as illustrated in FIG. 11, internal electrodes 102 and 103 are exposed at an end surface 101a of a ceramic element assembly 101. The exposed portions of the internal electrodes 102 and 103 are typically recessed into the end surface 101a. A plating film is deposited on exposed portions 102a and 103a of the internal electrodes 102 and 103, and then grown. Therefore, even when the internal electrodes 102 and 103 are recessed into the end surface 101a, the plating film connecting the internal electrodes 102 and 103 is formed. Compared to an external electrode formation method using a conductive paste, the external electrode formation method using a plating film produces thin and flat external electrodes.
According to the external electrode formation method using a conductive paste, bonding strength is increased by a glass component in the conductive paste. In contrast, there has been a problem with the above-mentioned plating method in that the fixing strength of the plating film to the ceramic element assembly is relatively low.
Therefore, in Japanese Unexamined Patent Application Publication No. 2006-332601, increasing the fixing strength of external electrodes by increasing the thickness of the internal electrodes in a portion where the internal electrodes are exposed has been disclosed.
In the structure described in Japanese Unexamined Patent Application Publication No. 2006-332601, the thickness of internal electrodes is relatively large in a portion where the internal electrodes are exposed. The relatively thickened portion is referred to as a thick film portion. When the thick film portion is provided, there have been problems in that the inner ends of the thick film portion are overlapped with the ends of the internal electrodes connected to other electric potentials through a ceramic layer or insulation resistance is varies in a portion where the inner ends of the thick film portion are adjacent to the ends of the internal electrodes connected to other electric potentials. This is caused by the fact that the inner ends of the thick film portion are blurred or indistinct when screen printing or other similar method is used to form the thick film portion. Therefore, a reduction in the variations in the properties of the laminated ceramic capacitor has not been achieved.